Selby Bangani Ngcobo was born in 1909 in Pietermaritzburg, the son of a mine compound foreman who later became a teacher and saddler, Ngcobo studied at Adams College, Fort Hare, the University of Natal, and Yale University, where he obtained an M.A. degree in 1940.
In 1957-1958 he was a British Commonwealth Fellow at London University, which in 1964 awarded him a Ph.D. in economics. While a student at the University of Natal he took an active part in the All African Convention (AAC)meeting of December 1935. He later served on the Africans' Claims committee but soon afterwards withdrew from political activity to concentrate on his academic career. He taught economics at Fort Hare and after 1959 at the University College of Rhodesia and the University of Botswana, Lesotho, and Swaziland.
In 1959 he served on the Molteno Commission, which made recommendations for the constitution of the Progressive Party. After retiring from UBLS he worked for the World Bank.
In July 1975 he returned to South Africa to become economic adviser to the KwaZulu Government of Mangosuthu Buthelezi, his former student.